Rotor for cutter-heads



G. L. KRABER. ROTOR FOR CUTTER HEADS. APPLICATION FILED N0v.2z. 191s.

1,396,762. Patented Nov. '15, 1921.

' J m INVENTOR.

15' 1 W 0 m 1k U O 1 a ATTORNEY.

. surfaces which it was planing.

of Oregon, have invented a certain UNITED STATES T 0 (w ll to ham it may concern:

Be it known that I, Gnome L. KRABER, a citizen of the United States, and a resident of Portland, county of Multnomah, State new and useful Improvement in Rotors for Cutter- Heads, of which the following is a specification. i

My invention relates to portable, pneumatic or air-driven tools; for example, a planer comprising a cutter-head having a rotor, or turbine, fixed on its axle, the rotor being provided with peripheral pockets to receive the impingement of a jet, or jets, of

the driving fluid, usuallycompressed air. 1n the making of these tools it washeretofore thought essential that the rotor be given considerable peripheral mass, inorder that it would develop momentum, and in this way carry it over the hard slpotsin the at I have discovered that the benefit of the momentum so gamed was atthe expense of acceleration;

in other words, it required an appreciable interval of time for the rotor to attain its maximum speed, and to regain its high speed, when slowed downbythe work 1mposed upon it. And, furthermore, since these tools are run at a yery highs eed,

considerable gyroscopic action was reveloped, due to the peripheral mass of the rotor, so that it imposed considerable muscular exertion on the operator in holding the planer to its work; especially when the tool is used on the sides of a vessel; for which work it is particularly intended.

I further discovered in my experimentation, that the momentum attained by the mass of the rotor may be considered a negligible factor, if the rotor be rendered more susceptible to acceleration so as to develop maximum speed in an instant.

Susceptibility to acceleration is essential because the maximum operative speed of the planer should be attained immediately after the air is turned on. The high speed of the cutter-head is depended upon for efficiency, because the work done consists in cutting away minute particles of the surface at a time; and if the tool encounters hard spots in the surface, and the extra work so imposed reduces its speed, such effect is negligible, provided its operative speed can be recovered by an instant of rest.

.In other words, the operator, when be en- Specification of Letters fatent.

PATENT, OFFICE- Gnonenn KRABER, or PORTLAND, OREGORlASSiGNOR, BY MESINE ASSIGNMENTS TO THE TURBINE AIR TOOLCOMPANY, or CLEVELAND, OHIO, A CORPORATION 1 ROTOR FOR CUTTER-HEADS.

Patented Nov. 15,1921.

Applicationflled November 27, 1918. Serial No. 264,385.

Acceleration is which occurs when the operator has finished his stroke in one direction and reverses the stroke.

Sincesusceptibility to acceleration is one of the conditions of efficiency, it is apparent that unnecessary mass in the part to be rotated introduces a corresponding factor of resistance to aceleration and of inefliciency.

I attain the desired results by reducing the mass, and thus the weight, of my rotor to a practical minimum; that is to say, I make my rotor of a material, aluminum for example, light in weight, and also make it of a shape tending to that end; in short, by the term practical minimum 1 mean the weight of the rotor shall be reduced as far as practical with regard to the factor of safety; so that, by retraining the same unit of driving force that it would have been practical to apply to a rotor of the same dimension but of greater mass, then by reducing the latter to a practical minimum increment in acceleration will be obtained. At the same time by reducing the mass of the rotor its gyroscopic action is greatly reduced, and the tool is rendered more easy to handle.

The embodiment of my invention in practice is illustrated in the accompanying drawings of a portable planer:

Figure 1 is a side elevation of this planer; Fig. 2 is a left-end sectional view with respect to Fig.1; and a Fig. 3 is a partial sectional side elevation. In a frame, a, is rotatably mounted a cut ter-head b cored out for lightness, and mounted on the threaded shoulders 0 of two rotors 03, one of which is located in each. side ofthe tool frame, and the cutter-head is mounted between them. The rotors cl are provided with stub-shafts e, revolving in ball-bearing rings f, in the central, annular recesses or boxes of the covers g, secured in place by nuts threaded on stud bolts g. Annular chambers h of the frame, a, extend circumferentially about the rotors, and annular bushings 7' provide fluid-tight closures for the open sides of the fluld chambers h offset in its bearing face Fig. 1, and such offset end extending circumferentially about and confining the driving fluid to the inlet ports r of said annular bushings I. A transverse passage-way 71 connect the annular chambers h.

I use compressed air as the driving force, and the source thereof is connected by a hose with the nipple m. y

The frame, a, is made with an integral handle it" in which islocated a valve for controlling the admission of the air fluid; only the projecting stem Z of said valve being shown.

The rotors (Z, instead of being made of a heavy material-as heretofore was the practice in order to obtain a fly-wheel effect are; made of aluminum, since the latter is at resent the lightest material deemed suitab e for making the rotors. The latter are also cored .out,"as at cl, in order to lighten them still more. v rotors are provided with an endless series ofpockets n for receiving the impact of the jets of compressed air admitted through theinlet ports r from the annular chambers h-; a plurality of inlet ports being provided, and the same spaced equal distanoes apart.

The cutter-head is inclosed by a hood 8, having a spout t for discharging the shav- IIIOS. r it the end a of the frame the latter is from a straight line and preferably at an angle, as shown in is covered by an adjustable shoe 0, the body of the frame bya screw 70 threaded into the frame and provided with a lock nut Q. r

But the details of construction of my tool The peripheries of the adjustable relatively toare immaterial; my invention merely has for its purpose the carryin into practice of my discovery that in orc or to have an efficient portable tool of the character described it is essential that the weight or mass of the rotor, or turbine, be reduced to a practical minimum, so as to reduce to a negligible factor the gyroscopic effects and obtain an increment in acceleration from the given unit of driving. force, so that the cutter-head may attain and regain its maximum speed in an instant.

The desired new results attained in my improved rotor may be contributed to by avoiding unnecessary mass in the making of the driven part, that is, the cutter-l1ead.

I claim:

1. In a portable fluid driven tool of the character described designed to be manually applied to the work, a rotor made of a light metal thereby adapting the rotor to greater acceleration relatively to a given unit of driving force, and rendering its gyroscopie action a negligible factor.

2. In a portable fluid driven tool of the character described designed to be manually applied to the work, a rotor made of aluminum thereby adapting the rotor to greater acceleration relatively to a given unit of driving force, and rendering its gyroscopic action a negligible factor.

3. In a portable fluid driven tool of the character described, designed to be manually applied to the work, a rotor made of aluminum, cored out and lightened to adapt the rotor to greater acceleration relatively to a given unit of driving force, and to reduce its fly wheel action and to render its gyroscopic action a negligible factor.

GEORGE L. KRABER. 

